Intraspecific trait variability is a key feature underlying high Arctic plant community resistance to climate warming

Abstract

In the high Arctic, plant community species composition generally responds slowly to climate warming, whereas less is known about the community functional trait responses and consequences for ecosystem functioning. The slow species turnover and large distribution ranges of many Arctic plant species suggest a significant role of intraspecific trait variability in functional responses to climate change. Here we compare taxonomic and functional community compositional responses to a long‐term (17‐year) warming experiment in Svalbard, Norway, replicated across three major high Arctic habitats shaped by topography and contrasting snow regimes. We observed taxonomic compositional changes in all plant communities over time. Still, responses to experimental warming were minor and most pronounced in the drier habitats with relatively early snowmelt timing and long growing seasons (Cassiope and Dryas heaths). The habitats were clearly separated in functional trait space, defined by 12 size‐ and leaf economics‐related traits, primarily due to interspecific trait variation. Functional traits also responded to experimental warming, most prominently in the Dryas heath and mostly due to intraspecific trait variation. Leaf area and mass increased and leaf δ15N decreased in response to the warming treatment. Intraspecific trait variability ranged between 30% and 71% of the total trait variation, reflecting the functional resilience of those communities, dominated by long‐lived plants, due to either phenotypic plasticity or genotypic variation, which most likely underlies the observed resistance of high Arctic vegetation to climate warming. We further explored the consequences of trait variability for ecosystem functioning by measuring peak season CO2 fluxes. Together, environmental, taxonomic, and functional trait variables explained a large proportion of the variation in net ecosystem exchange (NEE), which increased when intraspecific trait variation was accounted for. In contrast, even though ecosystem respiration and gross ecosystem production both increased in response to warming across habitats, they were mainly driven by the direct kinetic impacts of temperature on plant physiology and biochemical processes. Our study shows that long‐term experimental warming has a modest but significant effect on plant community functional trait composition and suggests that intraspecific trait variability is a key feature underlying high Arctic ecosystem resistance to climate warming.

Three decades of environmental change studies at alpine Finse, Norway: climate trends and responses across ecological scales

“…Although individual plant species (Klanderud, 2008) and plant community functional composition (van Zuijlen et al 2021b) responded to experimental warming at Finse, the effect on the Dryas heath plant community species composition was limited Totland, 2005b, Hasvik, 2018), suggesting that the community is relatively resistant to changes in temperature. This is in line with findings from other ITEX sites (e.g., Hudson and Henry (2010), Lamb et al (2011), Jónsdóttir et al (2022, personal communications) and could be related to climatic context , i.e., that responses are less pronounced at sites with drier conditions (Elmendorf et al, 2012b, Scharn et al, 2022. In addition, the Dryas heath at the Finse ITEX site is relatively species rich (on average approx.…”

Increases in functional diversity of mountain plant communities is mainly driven by species turnover under climate change

“…As an example, intraspecific trait variation (ITV) was found greater in species with large range sizes and lower median elevations (Rixen et al 2022). High ITV likely leads to an increased capability to respond to climate warming (Jónsdóttir et al 2022). In contrast, small ranged species are expected to suffer from climatic changes as their ability to track climate change is limited through low ITV.…”

Bootstrapping outperforms community‐weighted approaches for estimating the shapes of phenotypic distributions

“…Traits vary within species due to ontogeny, abiotic forces, biotic interactions, experimental treatments and genetic differences, and thus, average traits may be a poor approximation for the traits of an individual (Agrawal, 2001; Bolnick et al, 2011; Finney et al, 2002; Hendry, 2016; Miner et al, 2005; Parmesan & Yohe, 2003; Reznick & Ghalambor, 2001; Violle et al, 2012). Population biologists and ecologists have, therefore, increasingly come to realize that locally measured traits, along with the representation of intraspecific trait variation, are essential and can better reveal the local ecological and evolutionary processes that shape local communities (Bolnick et al, 2003, 2011; Fontana et al, 2018; Hart et al, 2016; Jónsdóttir et al, 2022; Lake & Ostling, 2009; Siefert et al, 2015; Uriarte & Menge, 2018; Violle et al, 2012). Furthermore, using average species traits leads to statistical non‐independence between sites that share species, inflating Type 1 errors when using standard regression techniques (Miller et al, 2018).…”

“…Although bootstrapping methods are becoming increasingly common in the trait‐based literature (Enquist et al, 2017; Gaüzère et al, 2019; Henn et al, 2018; Jónsdóttir et al, 2022; Ross et al, 2017), we currently lack a clear picture of the relative performance of these methods and how much common sampling strategies impact those performances. Here, we test the accuracy of different methods to estimate the four moments of trait distributions.…”